JPH0457054A - Electrostatic recording body - Google Patents

Abstract

PURPOSE:To obtain a recording body having superior curl resistance and holding a high density image by specifying the coating weight of a dielectric layer and a resin component in the layer. CONSTITUTION:A copolymer of methacrylic acid with alkyl methacrylate or a copolymer of methacrylic acid with alkyl methacrylate and other monomer is used as a resin component in a dielectric layer 3. The glass transition temp. of the resin component is 10-30 deg.C. It is necessary that the resin component accounts for 40-60wt.% of the amt. of the layer 3 and the remainder is based on a pigment 4. The layer 3 is formed by 3-6g/m<2>, voltage is impressed on the layer 3 and an electrostatic latent image is formed in accordance with an original signal, developed with a wet toner and fixed.

Description

[Detailed description of the invention] [Industrial application field] The present invention relates to an electrostatic recording medium, and in particular, CAD (C.

The present invention relates to an electrostatic recording medium that is particularly useful for wet development systems, such as electrostatic printers used in plotters and facsimile machines.

[Conventional technology]

Electrostatic recording media generally consist of a dielectric layer made of high-resistance resin provided on a conductive support, and an electrostatic image is formed by directly charging the surface of the dielectric layer with an electric field corresponding to the original using a recording needle or the like. After this electrostatic charge image is visualized with a developer, it is fixed to obtain a permanent visible image.

Conventionally, the high-resistance resin used for the dielectric layer of electrostatic recording materials is
There were alkyd resins, silicone resins, epoxy resins, polyvinyl acetal resins, polyurethane resins, vinyl acetate resins, vinyl chloride resins, acrylic acid ester resins, styrene-butadiene resins, etc., and these resins were used as dielectric layers of electrostatic recording materials. Required characteristics (e.g., ability to charge to a high potential, small attenuation of potential after charging,
However, it has not always been possible to obtain a high-density and clear image upon development, to have good curl resistance and blocking resistance, etc.).

In view of these circumstances, a specific copolymer resin (one or more monomers from a certain group and one or more monomers from another group is copolymerized to form a dielectric layer with a glass transition temperature of 10 to 50 It has been proposed to use copolymer resins (copolymer resins at temperatures of 10 to 10 °C) (publications such as Japanese Patent Publication No. 5746064, Japanese Patent Publication No. 57-46065, and Japanese Patent Publication No. 57-46066).

Incidentally, in recent years, CAD has become popular, and electrostatic recording type printer plotters are attracting attention, particularly in terms of speed and resolution. A cutter is partially attached to an electrostatic printer plotter, and if the curl of the electrostatic recording paper on which an image is formed increases toward the face side, there is a tendency for a jam to occur in a portion of the cutter. Therefore, in addition to the above-mentioned characteristics, it has become important to suppress face curl as much as possible for the quality of electrostatic recording paper.

[Problem to be solved by the invention]

The present invention provides an electrostatic recording medium which is designed to minimize face curl, eliminate jams in electrostatic printer plotters, and provide good handling properties for drawing inspection and the like.

[Means to solve the problem]

The present invention provides an electrostatic recording material in which a dielectric layer is provided on a conductive support, in which the amount of the dielectric layer adhered is 3 to 6 g/m2, and the resin component of the dielectric layer is methacrylic acid and methacrylic acid. A copolymer with alkyl or a copolymer containing these monomers as a polymerization component, which has a glass transition temperature (Tg) of 10 to 30°C, and this copolymer has a glass transition temperature (Tg) of 40 to 30°C in the dielectric layer. 60% by weight, and the rest is mainly composed of pigments.

The present invention was made with the intention of preventing the curl of an electrostatic recording material from changing significantly even with changes in humidity by providing a dielectric layer that is amenable to the expansion and contraction of a conductive substrate.

As mentioned earlier, electrostatic recording materials are generally made by providing a dielectric layer on a conductive substrate obtained by directly coating or impregnating a conductive substance such as a polymer electrolyte onto a support such as paper. It is. The conductive substrate is a water-based coating, and considering its expansion and contraction in response to changes in humidity, it is thought to be considerably larger than the dielectric layer.

When a dielectric layer with good chargeability is provided on such a normal conductive substrate, a very large face curl occurs, especially at high temperatures. This phenomenon occurs because the dielectric layer cannot keep up with the elongation of the conductive substrate. On the other hand, at low humidity, backcurl occurs, which is a phenomenon that occurs because the dielectric layer cannot keep up with the shrinkage of the conductive substrate.

However, some electrostatic recording materials are seen that have face curls at low humidity, but upon closer inspection, the amount of polymer electrolyte in the pre-coat (pre-low resistance layer) is larger than that in the back-coat layer (back low-resistance layer). If it is included,
It is thought that the conductive substrate itself curls toward the face side because the precoat side shrinks more than the backcoat side.

Therefore, the concept of providing a dielectric layer that is amenable to expansion and contraction of the conductive substrate of the present invention is different from the concept of simply using a flexible resin with a low glass transition temperature for the dielectric layer.

FIGS. 1, 2, and 3 schematically show three representative dielectric recording bodies according to the present invention.

That is, FIG. 1 shows a case in which a dielectric layer 3 is provided on the surface of a conductive substrate 5, and FIG. 3, conductive layers 21 and 22 are provided on both surfaces of a conductive substrate 5, and a dielectric layer 3 is provided on the conductive layer 21. In FIG.

In the figure, 4 represents a pigment.

The substrate 1, conductive layer 2, and conductive substrate 5 in the present invention are all no different from those conventionally used or known in the field of electrostatic recording materials.

For example, for the base 1, plain paper, transparent paper, etc. are used. For conductivity [2], 22, polymer electrolytes such as polyvinylbenzyltrimethylammonium chloride and ammonium polystyrene sulfonate, conductive zinc oxide, tin oxide, etc. are used.

The resin in the dielectric layer 3 is: (1) a methacrylic acid-alkyl methacrylate copolymer, (2) a copolymer consisting of methacrylic acid-alkyl methacrylate-monomer thereof, or (2) the above-mentioned (2).
Alternatively, a mixture of the copolymer (2) and its modified polymer may be used. Here, with alkyl methacrylate “
"Alkyl" has about 1 to 5 carbon atoms, with 4 carbon atoms being particularly desirable. Further, examples of the "other monomer" or "other polymer" include monomers and polymers such as styrene, vinyl acetate, and vinyl chloride.

In the above copolymer (2), the proportion (weight ratio) of the "other monomer" component in the copolymer is 30% or less, preferably 10%.
% or less. The proportion (weight ratio) of the methacrylic acid component and the alkyl methacrylate component in the mixture of (1) above is 7.
It is 0% or more, preferably 90% or more.

Among those constituting the dielectric M3, the glass transition temperature (Tg) of the resin component (1) and/or (2) is 10 to 30°C.
, preferably in the range of 15 to 25°C. If the temperature is lower than 10°C, a problem will arise in blocking properties, and if it is higher than 30°C, face curl will become large in high humidity, which is undesirable. Glass transition temperature (Tg) is 20°C
Copolymers of methacrylic acid and alkyl methacrylate, or copolymers mainly composed of these monomers, have a low Tg and are flexible, so that when the conductive substrate expands and contracts due to humidity, the dielectric layer 3 becomes flexible. It is thought that the curling property is improved by being stretched and contracted obediently. Further, the resin component (1) and/or (2) must account for 40 to 60% by weight of the dielectric layer resin. If the weight is less than 40%, the binding power of the pigment will be weakened and black streaks will appear more easily.
If the weight is greater, the smoothness will be higher, and an appropriate gap between the recording needle and the dielectric layer will not be maintained, making it difficult for discharge to occur.

The dielectric layer 3 contains calcium carbonate, clay, fired clay, talc, titanium oxide, barium sulfate, silicon, etc., in order to keep the gap between the recording needle and the dielectric layer appropriate and to facilitate discharge, or to improve the ease of writing with a pencil. Pigments such as acid, zinc oxide, epoxy resin powder, melamine resin powder, urea resin powder etc.4
(Particle size distribution based on volume, average particle size 6μm: 4-7゜5
Advantageously, the content is between 60 and 40% by weight of 50% .mu.m.

The amount of the dielectric layer 3 deposited is 3 to 6 g/m, preferably 4 g/m.
~5g/rrF. If the amount of adhesion is less than 3 g/m, its role as a dielectric layer will be insufficient, and 6 g/rrf
If the amount is larger than this, the expansion and contraction rate of the dielectric layer decreases due to its thickness, so that it cannot keep up with the expansion and contraction of the conductive substrate, and face curl becomes large at high humidity, which is disadvantageous.

A voltage is applied to the dielectric layer thus formed using a stylus head (needle electrode) or the like to form an electrostatic latent image in accordance with the original signal, which is developed with wet toner, fixed, and visualized.

〔Example〕

Parts here are by weight.

Example 1 After heating this conductive substrate with a gear render, the dielectric layer coating solution described above was applied to one side with a wire bar so that the dry coating amount was about 5 g/removal, and dried at 100° C. for 1 minute. I made an electrostatic recorder.

Comparative Example 1 An electrostatic recording material was produced in exactly the same manner as in Example 1, except that the dielectric layer coating solution was coated with a wire bar so that the dry weight was about 7.5 g/m.

Comparative Example 2 A dielectric layer coating solution was prepared by mixing 110 parts of toluene as a resin for a dielectric layer and dispersing the mixture in an attritor for 10 minutes.

On the other hand, an electrostatic recording material was prepared in exactly the same manner as in Example 1 except that 55 g/rd of high-quality paper was used.

Example 2 A conductive substrate was obtained by impregnating a conductive liquid consisting of 100 parts of methanol and drying (dry deposition amount: about 6 g/I).

A dielectric layer coating solution was prepared by mixing 110 parts of toluene and dispersing the mixture in an attritor for 10 minutes.

On the other hand, Comparative Example 4 LR-347 ((methacrylic acid-methyl methacrylate-
Butyl methacrylate copolymer) manufactured by Mitsubishi Rayon Co., Ltd., Tg
An electrostatic recording medium was prepared in the same manner as in Example 2 except that a 40% toluene-IPA mixed solution was used at 39°C.

Example 3 Water
A conductive layer coating solution consisting of 45 parts was applied and dried to form conductive layers each having a dry coating weight of 8 g/ml'.

After gear rendering this conductive substrate, the above-mentioned dielectric layer coating solution was applied to one side with a wire bar so that the dry coating amount was about 5 g/♂, and dried at 100°C for 1 minute to form an electrostatic recording material. I made it.

Comparative Example 3 An electrostatic recording material was prepared in exactly the same manner as in Example 2, except that the dielectric layer coating solution was applied with a wire bar at a dry adhesion amount of about 7.0 g/%.

25 parts of NS#400 (calcium carbonate, manufactured by Nitto Funka Co., Ltd.) and 110 parts of toluene were mixed together and dispersed for 10 minutes using an attritor to prepare a dielectric layer coating solution.

This liquid was coated on one side of the same conductive substrate as in Example 2 so that the dry adhesion amount was about 5 g/rrr to prepare a dried electrostatic recording material.

Comparative Example 5 An electrostatic recording material was produced in exactly the same manner as in Example 3, except that the dielectric layer coating solution was applied with a wire bar so that the dry amount of the coating solution was about 7.5 g/m.

Comparative Example 6 SBA750 (manufactured by Sanyo Chemical, Tg=43°C, 3o%h
) An electrostatic recording material was prepared in the same manner as in Example 3 except that (methacrylic acid-butyl methacrylate-styrene copolymer) was used.

Comparative Example 7 LP-035 (manufactured by Nippon Gosei Co., Ltd., polyester, Tg=2) was used as the resin for the dielectric layer.
An electrostatic recording material was produced in exactly the same manner as in Example 3 except that a 0.30% toluene-MEK mixed solution was used.

Reference example 1 The conductive support used in Example 1 was prepared.

Reference example 2 The conductive support used in Example 2 was prepared.

(a) For Example 1 and Comparative Examples 1 and 2, VER5A
TEC8224F electrostatic printer plotter (double-sided control type)
The image was drawn using a single-sided control type). In addition, in order to examine curl characteristics in each environment, samples were cut into A-4 sizes and data were collected.

The results are shown in Table 1, and the face curl of the present invention was significantly improved, the image density was high, and the blocking resistance was also good.

These 8 types of electrostatic recording materials and 2 types of conductive supports [Effects of the Invention] As is clear from the description of the examples, the electrostatic recording material according to the present invention has excellent curling characteristics even when environmental changes occur. and,
It maintains high-density images and has no other side effects.

[Brief explanation of drawings]

1, 2 and 3 are schematic views of two sides of an electrostatic recording medium according to the present invention. 1...Substrate 21, 22...Conductive layer 3/Dielectric layer '4...Pigment 5...Conductive substrate patent applicant Rico Co., Ltd.

Claims (1)

[Claims] (1) In an electrostatic recording material in which a dielectric layer is provided on a conductive support, the amount of the dielectric layer adhered is 3 to 6 g/m^2, and the resin component of the dielectric layer is methacrylic acid and A copolymer with an alkyl methacrylate or a copolymer containing these monomers as a polymerization component with a glass transition temperature of 1
An electrostatic recording material characterized in that the copolymer accounts for 40 to 60% by weight of the dielectric layer, and the remainder is mainly composed of pigment.